I 2nd Kensignton wine market......plus they sell singles so you can try a few different ones and not worry about having 4 crappy beers left if they taste bad.
Me and my bro used to collect obscure beer bottles/cans and we used to go there for them.
EDIT: As im looking at this post it doesnt sound good. I sound homeless....buying single beers and collecting cans
<---and a brown paper bag...haha